This invention relates to a composition suitable for the manufacture of vinyl floor tile and, in particular, to a vinyl floor tile composition free of asbestos.
For many years, mineral-filled vinyl floor tiling has utilized asbestos among the mineral filling components. In addition to providing reinforcement in the finished product, such use of asbestos has been particularly advantageous where the vinyl asbestos tile is made in a continuous process with individual tiles being cut from a continuous web or sheet of vinyl asbestos. As detailed in U.S. Pat. No. 3,904,579 which is incorporated herein by reference, the strength of such a web at relatively high processing temperatures and its ability to adhere to calendering rolls is of considerable importance. Specifically, the web must have sufficient hot tensile strength, i.e., the proper amount of viscous flow and melt elasticity at processing temperatures, that the web may be sheeted, calendered, and transported without sporadic ripping, tearing, or excessive elongation during hot processing on the calendering line. Since fibrous fillers, such as asbestos, greatly increase the hot strength of a vinyl composition, they were used in the past whenever needed. A typical formulation of a vinyl-asbestos composition utilizes a minor portion of vinyl polymer resin (typically 12-15% by weight) and a major portion of mineral filler, typically comprising a mixture of about 60% (composition weight) calcium carbonate as a bulking filler and about 20% asbestos as a reinforcing filler. The remainder of the composition is made up of plasticizer, stabilizer, lubricant and pigment.
In recent years manufacturers have, with little apparent success, attempted to reformulate their tile compositions to eliminate asbestos. However, insofar as applicant is aware, these efforts have not heretofore produced a substitute for asbestos in the manufacture of floor tile which would permit the manufacture on existing production equipment of floor tile comparable to vinyl asbestos tile in quality and cost.
Accordingly, there is a need for an asbestos free vinyl composition which can be manufactured into satisfactory floor tile on existing continuous-web tile production equipment.